This invention relates to a process for preparing cationic carboxamide monomers and their polymers.
Cationic polyacrylamides are known to be excellent flocculants for the treatment of sewage and aqueous suspensions of other organic and inorganic particulates. Probably the best known cationic polyacrylamides are those prepared by reacting polyacrylamide with formaldehyde and a dialkylamine. See, for example, U.S. Pat. Nos. 2,328,901; 3,539,535 and 3,979,348 as well as Suen and Schiller in Industrial Engineering Chemistry, Vol. 49, pages 21-32 (1956). Unfortunately, the cationic polyacrylamides prepared by these processes exhibit undesirable amine odors and are less stable than desired for many applications.
Attempts have been made to prepare such cationic polyacrylamides from corresponding cationic monomers. See, for example, U.S. Pat. No. 3,256,140. The results of such attempts have not been entirely satisfactory due to the substantial amount of saturated impurities resulting from the addition of the amine reactant across the ethylenic group of the acrylamide.
It has also been observed that the cationic polyacrylamides prepared by polymerizing water-miscible cationic acrylamides in aqueous solution often contain substantial amounts of undesirable gelled or crosslinked materials. Similar problems, as well as problems caused by very viscous reaction mixtures, often arise when such water-miscible cationic polyacrylamides are converted to the quaternary derivatives in aqueous solution. Attempts to minimize these problems by carrying out said reactions in very dilute aqueous solutions have been unsatisfactory from an economic viewpoint.
In view of the aforementioned deficiencies of the prior art methods, it would be highly desirable to provide an economical process for preparing cationic carboxamides and polymers thereof which are odorless and essentially free of gelled products and other undesirable impurities.